A conventional lifting desk contains a first tube, a second tube fitted with the first tube to form a movable leg, and a hydraulic cylinder, wherein a body and a column of the hydraulic cylinder are connected on a top of the second tube and a bottom of the second tube respectively so that the column of the hydraulic retracts inward or expands outward to drive the second tube to extend upward or retracts downward, thus adjusting a height of a desktop.
Another conventional lifting desk is disclosed in TW Utility Model No. 103218945 and contains a first tube and a second tube fitted with the first tube to form a movable leg, multiple roller arranged on an inner rim of an upper end of the second tube so as to guide the second tube to lift and descend smoothly. The second tube has a base arranged on a lower end thereof, and a cylinder mounted in the movable leg so that a bottom of the body is fixed on the lower end of the second tube, and a top of the column is coupled with an upper end of the second tube. The upper end of the second tube is rotatably connected with a control rod by using a connection seat, and the control rod is operated to abut against the column of the cylinder so that the column retracts inward or expand outward, and the movable leg is driven by the column to extend or retract, thus adjusting a height of a desktop.
To lift or descend the second tube stably after the cylinder actuates the second tube, the multiple rollers of the first tube contacts with an outer surface of the second tube, but the multiple rollers cannot contact with the outer surface of the second tube matingly, thus moving the second tube unstably. In addition, the multiple rollers are broken after a period of using time, so it is necessary to adjust or replace the multiple rollers.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.